Notch filter

Discussion in 'The Projects Forum' started by valdo1813, May 11, 2014.

  1. valdo1813

    Thread Starter New Member

    May 11, 2014
    1
    0
    HI, thanks for your time, I'm trying to design a notch filter with a cutoff frequency of 60 hz. So I decided to use a single band pass filter 60 hz and then use an opamp to subtract the signal and thus have a notch filter, but the output instead of the desired output, I get the signal with gain 10 (wich its my gain on desing of single band pass filter) more the input signal. I hope your support and thank you very much for your time. sorry for my english im from mexico :(




    red= first filter (single band pass filter 60 hz with 10 gain)
    green= original signal
    blue= output from substract
    esquematico.png

    grafica.png
     
  2. #12

    Expert

    Nov 30, 2010
    16,284
    6,797
  3. crutschow

    Expert

    Mar 14, 2008
    13,009
    3,233
    The bandpass amp has positive feedback so I don't see how that can work.

    Note that when subtracting the two signals you need to account for the phase-shift that the bandpass filter generates, which affects the subtraction result.
     
    #12 likes this.
  4. #12

    Expert

    Nov 30, 2010
    16,284
    6,797
    Thanks. I couldn't see how to fix what's wrong with that, so I just posted some images of circuits that will probably work.
    Valdo: You might describe what your end goal is and receive some good information.
     
Loading...